in late May 2012, Magdi Ragheb from the University of Illinois presented at the Thorium Energy Alliance Conference 4. He discussed his work on using electrostatic & electrodynamic neutron generators to operate or kick start LFTR style thorium reactors. As a neutron source, the polywell can either be used to breed all the needed U233 from thorium (so the LFTR need not also be a breeder), or can be used to simply kick start a LFTR which does its own breeding (such that no initial charge of Uranium or Plutonium is needed to begin breeding).

Lots of discussion and pics of polywell.

He concludes that even if the polywell by itself never hits positive Q, it can be used as-is as an excellent neutron source in conjunction with a LFTR. Combining the two allows for a hybrid fusion-fission reactor that can produce essentially unlimited energy.

While a LFTR is obviously not as clean as a working positive Q polywell burning pB11, such a hybrid system sure beats the heck out of burning coal. Running a LFTR using a polywell beats scrounging about for an initial load of enriched uranium to kick start a LFTR. Using a polywell as a neutron source to breed Thorium into U233 might well simplify the LFTR design.

Anyway, I'd never considered the idea of using a polywell simply as a neutron source leading to net power from a fission reaction. Interesting idea.

"Reality is that which, when you stop believing in it, doesn't go away."
--Philip K. Dick

Enginerd wrote:Anyway, I'd never considered the idea of using a polywell simply as a neutron source leading to net power from a fission reaction. Interesting idea.

I had also never before considered the idea that the polywell might present weapons proliferation issues. However it occurs to me that the bad guys could just as easily use a polywell as a neutron source to bombard Uranium 238 with neutrons, producing fissile Plutonium 239, which would be ideal for making bombs. Making a polywell into a neutron gun might take some money and some technical know how, but would be a minor task for a nation state determined to make weapons. Obtaining depleted uranium would presumably also not be particularly difficult for bad guys wanting to make weapons. Hmm...

"Reality is that which, when you stop believing in it, doesn't go away."

You would still need an initial load of fissile material. All the neutron source will do is make up for some neutron economy deficiencies. This may allow a high converter to become a break even breeder.
This might also allow using SNF with a high TRU, but there still needs to be a full fissile load.

KitemanSA wrote:You would still need an initial load of fissile material. All the neutron source will do is make up for some neutron economy deficiencies. This may allow a high converter to become a break even breeder.This might also allow using SNF with a high TRU, but there still needs to be a full fissile load.

Sure. But I can imagine the initial fissile load could itself be entirely produced at a factory using polywells to convert thorium left over from rare earth production into fissile U233, then separating the uranium from the thorium using chemical means.

I would imagine such a factory would have a number of advantages over mining many tons of natural uranium ore then needing to use centrifuges or SILEX to recover the needed amount of U235 (roughly 0.72% of natural uranium).

"Reality is that which, when you stop believing in it, doesn't go away."

Certainly. Just as the neutron flux while enriching uranium will irradiate the centrifuges, the factory equipment, the mining trucks, the ore crushers, etc. And leaves around tons and tons of mine tailings and depleted uranium. Fission is certainly messy.

Just as the neutron flux from D-D fusion and similar will irradiate the polywell device. Neutrons are messy when they go flying about.

Of course, it is all a matter of scale. Flattening mountains to dig up coal and then burning it by the gigaton is rather more messy. Yet that is precisely how the power I am using at my house is produced. At least the mess from neutron bombardment stays in one spot.

"Reality is that which, when you stop believing in it, doesn't go away."

KitemanSA wrote:You would still need an initial load of fissile material. All the neutron source will do is make up for some neutron economy deficiencies. This may allow a high converter to become a break even breeder.This might also allow using SNF with a high TRU, but there still needs to be a full fissile load.

Sure. But I can imagine the initial fissile load could itself be entirely produced at a factory using polywells to convert thorium left over from rare earth production into fissile U233, then separating the uranium from the thorium using chemical means.

Seems smarter to use the excess plutonium laying around and just use the neutron source for the small deficit due to excess minor actinides. IIRC the lead in time to create enough U233 would be decades. ICBW

When it comes to neutrons orders of magnitude matter. Mining trucks are not going to have any problem from them that anyone could reasonably notice. Background neutron flux from cosmic rays are about as significant. i.e. not at all.

KitemanSA wrote:Seems smarter to use the excess plutonium laying around and just use the neutron source for the small deficit due to excess minor actinides. IIRC the lead in time to create enough U233 would be decades. ICBW

I suppose it all depends on the rate at which the polywell machines being employed can produce neutrons. Obviously it would take eons if one were using a WB-6 class polywell. Lets imagine you had the money and intent for something on a more industrial scale...

Imagine a polywell in the WB-D/100 class. Even if such a polywell sadly proved to not produce net positive power, running it with D-T fuel, and with the device configured to emit neutrons as a jet, it could presumably make an insanely large number of neutrons and direct them where they were required. More than enough of a neutron flux I would imagine to run a factory producing U233 from thorium for use as reactor fuel. Or for a nation state with delusions of grandeur to convert U238 to Pu239.

"Reality is that which, when you stop believing in it, doesn't go away."

Looking more closely, starting around 15 minutes into the video, the pictures appear to show a Farnsworth–Hirsch style fusor rather than a polywell. Nearly all of the rest of his talk was all about the polywell, so I can only presume he must have some sort of a plan as to how to design or run a polywell to also produce a neutron jet.

Making a fusor produce a neutron jet also seems a pretty neat trick. Any idea how that is done?

"Reality is that which, when you stop believing in it, doesn't go away."

The stuff about 15-16 minutes in (thrusters) looks like George Miley's stuff at UIllinois.

The presenter Magdi Ragheb is from University of Illinois, so the connection would certainly make sense.

MSimon wrote:From what I understand the plasma is directed (thruster) but the neutron source is isotropic (quasi anyway). As you would expect because the plasma is charged.

Ok, that seems reasonable, though does put a major damper on the idea. As an isotropic neutron source, I suppose using it to breed fissile isotopes would require wrapping the device in a blanket of fertile material. That might somehow be doable, but presents a significant engineering challenge, given the power that would need to be dissipated from the interior.

EDIT: perhaps one could wrap the thing with a layer of graphite neutron reflecting material inside the coils, everywhere except one spot where neutrons are emitted.... Graphite could stand getting hot, and might even help protect the coils from neutron damage.

"Reality is that which, when you stop believing in it, doesn't go away."